In the production of semiconductor wafers, there are steps, such as a back-grinding step, in which semiconductor wafers are processed while their circuit pattern side is covered with a protective sheet applied thereto. In the back-grinding step, the semiconductor wafers which have undergone the step of forming a circuit pattern, e.g., an IC pattern, are ground or polished reduce their thicknesses to as thin as possible. For example, semiconductor wafers having a thickness of about 0.6 mm are ground to around 0.3 to 0.4 mm. The protective sheet in this step serves to prevent the semiconductor wafer from being broken and to prevent the circuit pattern side from being fouled or damaged by grinding dust or other substances. As illustrated in FIG. 1, an exemplary protective sheet. comprises a substrate sheet 12 made of a plastic film and a pressure-sensitive adhesive layer 13 formed thereon. Due to such construction, static electricity is apt to be generate and the protective sheet is apt to be electrostatically charged when the protective sheet is handled, such as when a separator 2 covering and protecting the pressure-sensitive adhesive layer 13 is peeled away or when the resulting protective sheet is applied to the circuit pattern side of a semiconductor wafer. Since the static charge accumulated on the protective sheet is discharged when the protective sheet is applied to a semiconductor wafer, sometimes resulting in breakage of the circuit pattern, some measures are being taken to prevent static buildup by imparting electrical conductivity to protective sheets by providing them with an antistatic layer 11, incorporating an electrically conductive powder, or by other suitable means.
When the protective sheet on a semiconductor wafer becomes unnecessary, it is stripped and removed from the circuit pattern side. This stripping also generates static electricity as in the above-described cases.
For this reason, the conventional method in which a worker strips off protective sheets directly by hand is problematic besides the poor working efficiency, the stripping of protective sheets may cause circuit breakage even if the protective sheets are electrically conductive because the static charges accumulated on the worker are also discharged.